At the time of forming and processing of sticky substances such as food products, adhesives, asphalt, tar, plastics, rubbers, and the like, various coating agents are used in order to prevent adhesion of the aforementioned sticky substances or contaminants to various substrates.
For example, various coating agents have been used for packaging materials for frozen meals; surface treatments for food preparation tools such as frying pans, toasters and the like; mold release agents for use in molds for forming plastics, rubbers and the like; interior treatments of paperboard containers for use in cooling and solidifying asphalt, tar and the like; and releasing agents for preventing adhesion between substrates coated by adhesives such as adhesive tapes, compression tapes, patches and the like. In addition, when recycled paper is produced by recycling waste paper, coating agents have also been used in order to prevent adhesion of various sticky components such as pitch, tar, ink and the like contained in waste paper, to press rolls, dryer rolls, canvases and the like of paper machines.
One of the aforementioned coating agents is a curable coating agent in which the coating agent is applied to a substrate, followed by curing to form a non-adhesive layer, and another is a non-curable coating agent in which the coating agent in the form of a liquid is applied to a substrate, as it is, to form a nonadhesive layer, followed by using, as it is, without curing. The aforementioned surface treatments, interior treatments and releasing agents are curable coating agents. On the other hand, the coating agents used in the step for producing recycled paper belong to non-curable coating agents. As the aforementioned mold release agents, both curable types and non-curable types are known.
As examples of non-curable coating agents, the following patent applications are published and known.
Japanese Unexamined Patent Application, First Publication No. H04-130190 discloses a lubricant for cleaning the surface of a paper dryer comprising an oil-based substance and a surfactant, in which examples of the oil-based substances include polybutene, machine oil, liquid paraffin and the like. However, in order to form a non-adhesive layer composed of the aforementioned oil-based substances, it is necessary to use a large amount of oil-based substances. For this reason, there are economical problems. Therefore, in Japanese Unexamined Patent Application, First Publication No. H07-292382, a silicone oil comprising a polydimethylsiloxane is used in order to obtain a sufficient non-adhesive layer while reducing the amount of the oil-based substances, as much as possible.
In the silicone oil of a polydimethylsiloxane, oxygen atoms of the siloxane main-chain thereof are oriented to the surface of a substrate, and the methyl groups binding to silicon atoms are oriented to the outside. For these reasons, when the silicone oil is applied to a substrate such as a press roll, a dryer roll, a canvas or the like of a paper machine, a non-adhesive layer formed from the aforementioned silicone oil can coat the surface of the substrate more strongly, but in fact, the silicone oil transfers to paper during the step of producing paper before reaching the aforementioned state. Thereby, sticky components in the waste paper may adhere to the surface of the aforementioned substrate.
Therefore, an approach has been proposed in which a silicone oil having a functional group is used instead of the silicone oils of polydimethylsiloxanes. For example, Japanese Unexamined Patent Application, First Publication No. 2000-96476 proposes that various silicone oils are applied to canvases in paper machines, in which examples of the aforementioned silicone oils include, in addition to a methylphenylsilicone oil and a diethylsilicone oil, an amino-modified silicone oil, an epoxy-modified silicone oil, and a higher fatty acid-modified silicone oil. In addition, Japanese Unexamined Patent Application, First Publication No. 2003-2135837 (Japanese Patent No. 3388450) proposes a method for preventing contamination on the surface of a dryer roll or canvas by means of forming a non-adhesive layer which is produced by spraying an oil-in-water (O/W) emulsion of an epoxy-modified silicone oil or an amino-modified silicone oil on the surface of a dryer roll or canvas during the step of producing paper.